Hellevator

A Hellevator (or Hellvator) is a continuous, often straight "mine shaft" allowing a character to "fall" all the way from the surface to The Underworld uninterrupted. This allows fast access to all layers. A hellevator can sometimes be annoying because of the random pools of water and lava you might dig into. To avoid this, place foreground walls, kind of like the foreground walls of the natural dug one, in the lava or water, then drain the liquid inside using buckets.

Terraria Hellevator

Construction

The Hellevator is not often built all at once. Generally, it is slowly built down through the Layers as the character(s) progress the game as a means to get ores and treasures. They are typically 2 or 3 blocks wide with many horizontal tunnels branching from them.

Recommendations

Protection: Protecting the tunnel from enemies with blocks on either side even through large caves is recommended so that traveling characters do not end up being attacked (and potentially knocked off the shaft's path). Doors where there are horizontal tunnels is also a good idea as it prevents monsters from walking into the shaft and falling with the character. Background Walls may also be placed to prevent mobs from spawning in the tunnel, though, this is extreme, especially in large worlds.

Lighting: Lighting, typically Torches, helps a player know in what part of the shaft his character is as well as illuminating enemies and collectables. Choose one side of the shaft to place them.

Rope: A character can travel down a rope or chain as fast as falling with out suffering fall damage upon hitting the bottom. Further more, little effort is needed to move back up. Choose the opposite side of the shaft from the lighting to place the rope as they are on the same Placement Layers

Check Points: Having a check point or outpost at the top or bottom of each level with a bed, campfire, a few Chests with basic needs, and doors allow a character to respawn where he is working without having to travel back every time for being killed or disconnected in Multiplayer. It also serves to provide a hiding place from enemies for low health characters.

Clear Liquids: Remove all liquids along the Hellevator. This is perhaps the most tedious part of the construction, but well worth the effort. Water can be blocked off and drained, but Lava will either need extensive effort to move, or be made into Obsidian and mined through. This can be achieved by letting water flow into the Hellevator, and then digging away at the obsidian as the water strikes the lava.

Catchers

If rope is not used, one of the following options is available:

2 blocks deep of Water at the bottom, just before the Underworld begins, otherwise if water is placed in the underworld it will drain and disappear in a few seconds.

1 or more Cobwebs at or near the end, however the cobweb will need to be replaced, as it is broken if the player stays in it for too long or swings at it with any tool.